Measurement of rotary pump flow and pressure by computation of driving motor power and speed

Abstract

Measurement of pump flow and pressure by ventricular assist is an important process, but difficult to achieve. On one hand, the pump flow and pressure are indicators of pump performance and the physiologic status of the receptor, meanwhile providing a control basis of the blood pump itself. On the other hand, the direct measurement forces the receptor to connect with a flow meter and a manometer, and the sensors of these meters may cause haematological problems and increase the danger of infection. A novel method for measuring flow rate and pressure of rotary pump has been developed recently. First the pump performs at several rotating speeds, and at each speed the flow rate, pump head and the motor power (voltage x current) are recorded and shown in diagrams, thus obtaining P (motor power) - Q (pump volume) curves as well as P - H (pump head) curves. Secondly, the P, n (rotating speed) values are loaded into the input layer of a 3-layer BP (back propagation) neural network and the Q and H values into the output layer, to convert P-Q and P-H relations into Q=f (P,n) and H=g (P, n) functions. Thirdly, these functions are stored by computer to establish a database as an archive of this pump. Finally, the pump flow and pressure can be computed from motor power and speed during animal experiments or clinical trials. This new method was used in the authors' impeller pump. The results demonstrated that the error for pump head was less than 2% and that for pump flow was under 5%, so its accuracy is better than that of non-invasive measuring methods.